1. Field of the Invention
This invention relates to organopolysiloxane compositions which cure upon exposure to ultraviolet radiation or upon contact with moisture into silicone rubber products having improved physical properties and are thus useful as adhesives, sealants, coating agents, potting agents and the like. It also relates to cured products of the compositions and a method for preparing the compositions.
2. Prior Art
Most prior art moisture-curable compositions are of one-part type and cure upon contact with moisture in the air by simply extruding from containers such as tubes and cartridges. Because of such ease of application and no attack on electric and electronic parts, they are universally used in the electric, electronic and building fields.
However, since the moisture-curable organopolysiloxane compositions cure upon contact with moisture in the air, it takes a long time for curing to proceed from the surface to the deep interior when the compositions are extruded in the air from the tubes or cartridges. Because of slow curing to the deep interior, the moisture-curable organopolysiloxane compositions would be rather deleterious to the speedup of the part production line when used for bonding, sealing or coating of electronic parts. There is a need for improvement in this regard.
Also, ultraviolet (UV) radiation-curable organopolysiloxane compositions are well known in the art. Japanese Patent Publication (JP-B) No. 40334/1977 or U.S. Pat. No. 4,064,027 and Japanese Patent Application Kokai (JP-A) No. 104158/1985 disclose mixtures of a vinyl-containing organopolysiloxane and a mercapto-containing organopolysiloxane which undergo photo-addition for curing upon exposure to UV. These compositions have satisfactory curing capabilities, but suffer from the problems of disgusting odor and metal corrosion due to the use of mercapto-containing organopolysiloxane. Their application to electric and electronic parts is thus not recommended.
It is also proposed in JP-B 36515/1978 and JP-A 215009/1985 or U.S. Pat. No. 4,675,346 to incorporate sensitizing agents with acryl-containing organopolysiloxane such that the resultant compositions are UV curable. These compositions, however, are less curable especially at the surface. Only resinous compositions having increased acryl contents provide smooth curing. There remains a problem of UV curing capability.
There is a desire to have a curable organopolysiloxane composition which is easy to apply and can quickly cure from the surface to the deep interior.